Visual perception and action Flashcards
Whats perception?
The sensory experience of the world. It involves both recognizing environmental stimuli and actions in response to these stimuli.
What do we gain through the perceptional process?
we gain information about the properties and elements of the environment that are critical to our survival.
2 things perception lets us do
creates our experience of the world around us;
it allows us to act within our environment.
how we receive info from the environment?
we are equipped with five sensory organs (eyes, ears, nose, mouth, touch)
Each receives raw sensory input from the external world that it transmits it to the brain
what can perception be thought as?
as the basic cognitive process that analyzes and makes sense of information from the sens
whats sensation?
The ability of our senses to detect various forms of energy (light or sound waves for example)
To sense does not involve making sense of the input.
whats perception?
Making sense of the raw sensory input
where is info transmitted down from? and to where?
visual cortex (back of the brain) to two relatively independent visual pathways
what are these pathways called?
The ventral (or “what”) pathway is responsible for processing colour and form•
The dorsal (“where”) pathway is responsible for movement and spatial relations
What was historically thought of what the visual system provided us with?
an internal (and conscious) representation of the external world (allowing us to recognize)
what did rival theorists suggest instead?
suggested the aim of the visual system was to facilitate our interaction with the world
what did Milner & Goodale (1995; 2008) instead argue for?
two visual systems each fulfilling a different function:
- One which is focused on providing an internal representation of the world;
- One that is focused on action and interaction with the world
What’s the vision for the perception stream? Milner & Goodale (1995; 2008)
based on the ventral stream. Used to decide whether an object is a cat, or a buffalo or when admiring a landscape. Role – to identify objects
What’s a Vision-for-action system? Milner & Goodale (1995; 2008)
based on the dorsal stream and used for visually guided action (i.e., interactions with the environment)
What’s bottom-up processing in perception?
Physical characteristics of stimuli drive perception (in other words, top-down processing is not needed for perception, the stimulus is enough).
Top-down processing in perception:
Knowledge, expectations, thoughts, past experiences guide perception (in other words, the stimulus is not enough, we must work on the image arriving on the retina to make sense of it)
Gibson’s(1979) Theory of Direct Perception
- vision for action - what approach?
Primarily bottom-up
Gregory’s(1970) Constructivist Theory of Perception
-visison for recognition
primarily top-down
Milner & Goodale’s(1998) Perception-Action Mode
- vision for recognition and action
Both top-down and bottom up
Gibsons theory of direction perception
- whats bottom up?
whats action driven?
bottom-up: Perception takes place directly from the environmental input. There is no need to work on the image arriving on the retina (i.e., no top-down processing required)
•Action driven: The end point (or purpose) of perception is to enable interactions with the real word
what did gibson argue?
that vision developed so our ancestors could respond rapidly to the environmen
what type of apporach did gibson go with?
An Ecological Approach:
•Perception should be studied by determining how the real environment structures the light that reaches our retina (the ambient optic array, described next)•
He did not agree with laboratory based investigations of perception using images (often line drawings) presented in a 2D plane
how do we take useful info about the environment?
about the environment directly from the light waves that reach our eyes
- Important theory elements:
- Ambient optic array
- Invariants
- Optic Flow
- Affordances
Whats the ambient optic array?
Structure is imposed on light waves that are refracted by the textured surfaces in the world around us.
- The light reflected from surfaces in the environment converges at the point in space occupied by the observer.
- As you move, the position of your head with respect to the environment is altered and the optic array changes accordingly.